feat: add test suite, fix backend bugs, remove legacy artifacts 🧪

- Add 73-test suite across conftest, utils, admin API, reconciler, zone parser,
  and CoreDNS MySQL backend (all green, ~0.5s)
- Fix zone_exists filter using wrong column name (name → zone_name)
- Fix delete_zone missing dot_fqdn normalization on lookup
- Remove spurious unused `from config import config` in coredns_mysql.py
- Fix config loader to search module-relative path so tests find app.yml
  without needing a root-level config/ directory
- Remove legacy v1 Flask prototype (app.py), empty config.json, and
  duplicate root config/app.yml

tests/test_coredns_mysql.py

@@ -1,47 +1,158 @@
+"""Tests for the CoreDNS MySQL backend (run against in-memory SQLite)."""
 import pytest
 from sqlalchemy import create_engine
 from sqlalchemy.orm import scoped_session, sessionmaker
 
-from directdnsonly.app.backends.coredns_mysql import CoreDNSMySQLBackend, CoreDNSRecord
-from loguru import logger
+from directdnsonly.app.backends.coredns_mysql import (
+    Base,
+    CoreDNSMySQLBackend,
+    Record,
+    Zone,
+)
+
+
+# ---------------------------------------------------------------------------
+# Fixture — in-memory SQLite backend (bypasses real MySQL connection)
+# ---------------------------------------------------------------------------
 
 
 @pytest.fixture
-def mysql_backend(tmp_path):
-    # Setup in-memory SQLite for testing (replace with test MySQL in CI)
+def mysql_backend():
     engine = create_engine("sqlite:///:memory:")
-    CoreDNSRecord.metadata.create_all(engine)
+    Base.metadata.create_all(engine)
 
-    class TestBackend(CoreDNSMySQLBackend):
+    class _TestBackend(CoreDNSMySQLBackend):
         def __init__(self):
-            super().__init__()
+            # Manually initialise without triggering the MySQL create_engine call
+            self.config = {}
+            self.instance_name = "test"
             self.engine = engine
             self.Session = scoped_session(sessionmaker(bind=engine))
 
-    yield TestBackend()
+    yield _TestBackend()
     engine.dispose()
 
 
-def test_zone_operations(mysql_backend):
-    zone_data = """
+# ---------------------------------------------------------------------------
+# write_zone / zone_exists / delete_zone
+# ---------------------------------------------------------------------------
+
+
+ZONE_DATA = """\
+$ORIGIN example.com.
+$TTL 300
 example.com. 300 IN SOA ns.example.com. admin.example.com. (2023 3600 1800 604800 86400)
 example.com. 300 IN A 192.0.2.1
 """
-    # Test zone creation
-    assert mysql_backend.write_zone("example.com", zone_data)
+
+
+def test_write_zone_creates_zone(mysql_backend):
+    assert mysql_backend.write_zone("example.com", ZONE_DATA)
+
+
+def test_zone_exists_after_write(mysql_backend):
+    mysql_backend.write_zone("example.com", ZONE_DATA)
     assert mysql_backend.zone_exists("example.com")
 
-    # Test record update
-    updated_zone = """
+
+def test_zone_does_not_exist_before_write(mysql_backend):
+    assert not mysql_backend.zone_exists("missing.com")
+
+
+def test_write_zone_idempotent(mysql_backend):
+    assert mysql_backend.write_zone("example.com", ZONE_DATA)
+    assert mysql_backend.write_zone("example.com", ZONE_DATA)
+
+
+def test_write_zone_updates_records(mysql_backend):
+    mysql_backend.write_zone("example.com", ZONE_DATA)
+
+    updated = """\
+$ORIGIN example.com.
+$TTL 300
 example.com. 3600 IN A 192.0.2.1
 example.com. 300 IN AAAA 2001:db8::1
 """
-    assert mysql_backend.write_zone("example.com", updated_zone)
+    assert mysql_backend.write_zone("example.com", updated)
 
-    # Test record removal
-    reduced_zone = "example.com. 300 IN A 192.0.2.1"
-    assert mysql_backend.write_zone("example.com", reduced_zone)
 
-    # Test zone deletion
+def test_write_zone_removes_stale_records(mysql_backend):
+    mysql_backend.write_zone("example.com", ZONE_DATA)
+
+    reduced = "example.com. 300 IN A 192.0.2.1"
+    mysql_backend.write_zone("example.com", reduced)
+
+    session = mysql_backend.Session()
+    zone = session.query(Zone).filter_by(zone_name="example.com.").first()
+    records = session.query(Record).filter_by(zone_id=zone.id, type="AAAA").all()
+    assert records == []
+    session.close()
+
+
+def test_delete_zone_removes_zone_and_records(mysql_backend):
+    mysql_backend.write_zone("example.com", ZONE_DATA)
     assert mysql_backend.delete_zone("example.com")
-    assert not mysql_backend.zone_exists("example.com")
+    assert not mysql_backend.zone_exists("example.com")
+
+
+def test_delete_nonexistent_zone_returns_false(mysql_backend):
+    assert not mysql_backend.delete_zone("ghost.com")
+
+
+def test_reload_zone_returns_true(mysql_backend):
+    assert mysql_backend.reload_zone("example.com")
+    assert mysql_backend.reload_zone()
+
+
+# ---------------------------------------------------------------------------
+# verify_zone_record_count
+# ---------------------------------------------------------------------------
+
+
+def test_verify_zone_record_count_match(mysql_backend):
+    mysql_backend.write_zone("example.com", ZONE_DATA)
+    # SOA + A = 2 records total
+    matches, count = mysql_backend.verify_zone_record_count("example.com", 2)
+    assert matches
+    assert count == 2
+
+
+def test_verify_zone_record_count_mismatch(mysql_backend):
+    mysql_backend.write_zone("example.com", ZONE_DATA)
+    matches, count = mysql_backend.verify_zone_record_count("example.com", 99)
+    assert not matches
+    assert count == 2
+
+
+def test_verify_zone_record_count_missing_zone(mysql_backend):
+    matches, count = mysql_backend.verify_zone_record_count("ghost.com", 0)
+    assert not matches
+    assert count == 0
+
+
+# ---------------------------------------------------------------------------
+# reconcile_zone_records
+# ---------------------------------------------------------------------------
+
+
+def test_reconcile_removes_extra_records(mysql_backend):
+    mysql_backend.write_zone("example.com", ZONE_DATA)
+
+    # Inject a phantom record directly into the DB
+    session = mysql_backend.Session()
+    zone = session.query(Zone).filter_by(zone_name="example.com.").first()
+    session.add(Record(zone_id=zone.id, hostname="phantom", type="A",
+                       data="10.0.0.99", ttl=300, online=True))
+    session.commit()
+    session.close()
+
+    success, removed = mysql_backend.reconcile_zone_records("example.com", ZONE_DATA)
+    assert success
+    assert removed == 1
+
+
+def test_reconcile_no_changes_when_zone_matches(mysql_backend):
+    mysql_backend.write_zone("example.com", ZONE_DATA)
+    success, removed = mysql_backend.reconcile_zone_records("example.com", ZONE_DATA)
+    assert success
+    assert removed == 0